Drawing Tutorial

This drawing tutorial was hosted by Matt Suski on 2020-06-25

Starting Off

Adjust the drawing details from the file properties. Don’t edit them directly!

To change the sheet scale, right-click the sheet and select properties.

Remember to take machining into consideration when designing. Engineers often over tolerance their drawings; be nice to your machinist!

When adding datums, keep in mind where you can measure from. They should be easy to measure from. Remember what the part mates to!

GD&T

In terms of machining, 100 microns in most GD&T cases are super reasonable. Tighten up if necessary.

Flatness: A common flatness reference is 100 microns, adjust based on needs. Bolt heads are garbage when it comes to flatness; even standard dimensions with no concern for flatness are good enough.

Perpendicularity: This is always in reference to another datum! Perpendicularity is a little complicated; be aware that you may have to use one or two datums depending on how you want to constrain it.

True Position: Consider that a hole should not be positioned relative to perpendicular axes, because this leads to a square tolerance for the hole center. Using true position turns our square tolerance zone into a circle, which is intuitively what we would want. This also implies perpendicularity.

Ordinate Dimensioning

A clean way to dimension is ordinate dimensioning, where our measurements overlap and are all relative to the appropriate datum. Make sure that you’re always dimensioning between a feature ad the datum, never feature-to-feature.

Hole Callouts

Fits

The ISO system sets out different classes of fits, from clearance to interference. You can read an ISO chart to find the necessary tolerance (usually a min and max). You can add this to the hole callout with a bilateral tolerance.

Finishing Up

Remember to add centerlines for holes! They are usually implied, but add clarity. Try not to obscure them with leader lines.

Try to use bent leaders for legibility.

You can use brackets to denote reference dimensions, which are absolutely non-critical. You can probably do this more often than you think!

Remember to reduce precision where it isn’t necessary. Refer to the standard precision in the drawing information.

Add hidden lines, it helps.

Try to get two other pairs of eyes on your drawings, but always at least one other.